<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /*#username {*/
        /*    !*background: url("../images/user_icon.png")no-repeat 315px ;*!*/
        /*    !*width: 350px;*!*/
        /*    !*height: 40px;*!*/
        /*    border-radius: 5px;*/
        /*    !*border: 1px solid #999999;*!*/
        /*    box-shadow: 1px 1px 3px #cccccc;*/
        /*    padding-left: 10px;*/
        /*    margin-right: 10px;*/
        /*}*/

        /*#username {*/
        /*    background: url("../dist/images/login.png") no-repeat 315px;*/
        /*    background-size: 315px;*/
        /*}*/
        /*background : background-color background-image background-repeat background-attachment background-position*/
        .user{
            background: url("../dist/images/login.png") no-repeat  5px 4px;
            /*background-image: url(../dist/images/login.png);!*设置小图标*!*/

            background-size: 25px 25px;/*小图标的大小*/

            /*background-position: 5px 4px;!*小图标在input的位置*!*/

            /*background-repeat: no-repeat;!*背景小图标不重复*!*/

            padding: 8px 10px 8px 40px;/*设置input内边距*/

            /*设置input样式好看*/
            border:1px solid #ddd;
            margin: 30px;
            width: 220px;

        }
    </style>
</head>
<body>
<div>
    <form>
        <input type="text" id="username" class="user">
    </form>
</div>
</body>
</html>